Aircraft heating apparatus



March 28, 1944 H. J. AUE N. MccoLLuM Erm. 2,345,140

* AIRCRAFT HEATING APPARATUS Filed Sept. 5,1942

' i i i i oVEEBaAED Patented Mar. 28, 1944y mimic FFICB HEATING APlFiRATUS Henry J. DeN. McCollum' and Imm A. Williams, Jr., Chicago, Ill.; said Williams as slgnor to Stewart-Warner Corporation, Chicago, Ill., a

corporation of Virginia Application September 3, 1942, Serial No. 457,1`52

scams. (cuasi-112.3)

Our invention relates generally to aircraft heating `apparatus and more particularly to means for controlling the operation oi such apparatus.

It has become common practice to utilize a portion of the fuel and air mixture supplied to 'the .aircraft engine by its supercharger as `a source of combustible mixture for the'operation/ oi' one or more internal combustion type heaters for heating the cabin and other parts of thev aircraft. The products of combustion from the heater have ordinarily been discharged overboard, but in some 'instances have. been returned to the inlet of the supercharger. Under some conditions of operationof the airplane it is desirableto utilize the differential pressurebetween the inlet and the outletjof the supercharger to cause dow of the combustible mixture to the Danying drawing, in whi Wer I0 of the internal combustion type is supheater and to 'cause the; discharge of the products 4 of combustion therefrom, while under other conditions of operation the pressure diierential between the pressure side of the supercharger and the atmosphere is suillcient for satisfactory op` eration of the heater. n

Although under substantially all conditions of airplane operation, the heater will operate satisfactorily when it is connected between the outlet and the inlet of the engine supercharger. there is a slight disadvantage in permanently connecting the heater in this manner. Even though the products of combustion entering the inlet of the supercharger form but a small perl centage of thel ow through the supercharger, and the dilutionY of the mixture supplied to the engines therefore does not noticeably affect engine operation, such-dilution must have some efl fect, and it is therefore advisable to avoid such admixture of the products of combustion from" the heater with the charg flowing to the engine whenever possible.

It is therefore an object of our invention to lprovide an improved means whereby the prod'- -ucts of combustion oi an internal combustion type heater may alternatively be discharged to the' atmosphere or to the inlet of the engine supercharger. Y

A further object is to provide .an improved means for automatically diverting the products of combustion from an internall -I combustion heater to cause these products to flow to the inlet description, reference becilng hadto the accom- Fig. 1 is a diagrammatic view of a operating a heater type: v

Fig. 2 is a diagrammatic form of such system; v Fig.l 3 is a central longitudinal sectional'view of the valve used in the system of Fig. l.

As shown diagrammatically in Fig. 1, a heatview of a modified plied with a combustible mixture through a conduit I2 from the high pressure side of a )supercharger M. The supex'charger Il is the` regular airplane supercharger used to supply the explosive mixture to the engine of the airplane through its discharge conduit i6. The mixture for the supercharger i4 is supplied thereto from a car;- hureting means through a conduit I8, the iiow through which is controlled by a throttle valve The products of combustion from the heater fiow therefrom through a discharge conduit 22. i

through a-'three-way diverter connection 2t. The

.connection 24 is adapted-,to conduct the flow of the engine supercharger whenever the;pres.

v sure differential between the outlet ofthe supercharger and the atmosphere is insuillcient to v.

assure satisfactory operation of the heater.

Other objects will appear from the following from the conduit 22 either through a conduit 26 ledmamto the conduit la or through a pipe.,

2l which leads overboard of the airplane,pref

erably at a point where the pressure is subatmospheric when the airplane is in ilight.

The heater I0 is of the internal combustion type, and may be of any suitable construction in which the burning gases andthe products of combustion are hermetically sealed trom the ventilating air, such, forexample, as shown in the copending application of Hr J. DeN. McCollum, Serial No. 447,345, led June 17. 1942.

The three-way connection 2l. as shown in Fig. 3, comprises a body 30 forming a T to one opening of which the conduit 22 is connected by suitable fittings. The other two openings in the body 30 are adapted to be closed by check valves 3l and 3,2, each comprising a seat 34, which may be in the form of a stamping held in place by a coupling fitting 36.- -A disc-shaped valve 38 is-guided forengagement with the seat 34 by a centering pin l0, which projects through' an aperture in a cross piece 4 2, which may be formed integrally with the valve seat 3,4.- 'I'he pin 40 also -serves to hold a spring-centeringvspider 43 to the rear face of the valve, this spider serving to hold v in place one end cfa conical compression' spring M the other end oi which is seated. against a i shoulder IB formed/in the coupling fitting Il.

.The valve seat stamping is clamped between lsystem for i v of the internal combustion a pair of annular gaskets 48,.upon screwing the coupling tting 33 in place.

The valves 3| and 32 may be constructed identically, except that the spring 44 of the valve 32 is preferably stronger than the spring- 44 of the valve 3|. For example, the spring for the valve 3| may be just strong enough to bias its valve disc 38 to closed position (when not subjected to pressure), irrespective of the position in which the valve 24 may be mounted in the airplane, while the spring for the valve 32 may be ,compressed suiiiciently so that this valve will open only when it is subjected to a predetermined differential pressure, in the order of 2" to 5" Hg., depending upon the characteristics of the engine and of the airplane: with which it is used. In the operation of the system of Figs. 1 and 3, the valve 3| will open to discharge the products of combustion from the heater overboard whenever the pressure within the valve 24 is slightly above atmospheric pressure, for example, .an inch or two of water above atmospheric pressure. Thus, whenever the supercharger |4 is supplying the mixture to the heater at a sufficiently high pressure to maintain the pressure within the body of valve 24 slightly above atmospheric pressure, the productsl of combustion will be discharged past the valve 3| to the atmosphere.'

There are many occasions when the absolute pressure at the inlet to the supercharger is below atmospheric pressure by an inch or two of mercury, while the pressure at the outlet of the supercharger is sufiiciently above atmospheric pressure for satisfactory operation of the' heater. Under these circumstances, it is desirable to continue to discharge the products lof combustion past the valve 3| to the atmosphere, and it is for this reason that the spring of the valve 32 is made suciently strong to prevent opening of the valve when these relative pressure conditions prevail. However, when the pressure at the outlet of the supercharger decreases to a value such that the. pressure in the body of the valve 24 is no longer slightly above atmospheric pressure, the valve 32 will open and the products of combustion from the heater thus discharged into the induction pipe I8 of the supercharger |4.

It will thus be .seen that the products of combustion from the heater will be discharged to the atmosphere whenever this manner of discharge of the time that the system is in operation.-

However, with the springs v44 of different strength, as described above, the products oi' combustion will be discharged to the atmosphere a greater proportion of the time than would be the case if the springs 44 were of equal strength.

It will be noted that when either the valve 3| or the valve 32 is open, the area of its valve disc 38 which is exposed to the pressure of the products of combustion in the valve body is increased, so that after one of the valves has been opened, it will tend to be held in open position It is not essential that there be this by the products of combustion flowing againstv and past it until the pressure differential upon its opposite sides becomes slightly less than that required to open the valve initially. From the foregoing, it will appear that irrespective ofthe operating conditions of the airplane and its engine, the heater will be maintained in operation, since the products of combustion vwill be withdrawn either through the 10 the relationship between atmospheric pressure and the pressures at the inlet and outlet of the supercharger.

It is not essential that the valve which diverts the products of combustion be automatically operable, since in some installations such diversion is required but infrequently. Under som'e operating conditions, and in some installations of the -heating system, the pilot will prefer to continue to have the products of combustion discharged overboard rather than diverting them to the inlet- .30 trated as having a hinged vane 52 operated by a handle 54. When in the position inwhich the vane 52 and handle 54 are shown in full lines in Fig. 2, the products of combustion will be discharged overboard through the conduit 28, whereas, when the vane 52 and handle 54 are moved to their dotted line. positions, the products of combustion will be discharged through the conduit 28 into the induction conduit I8 of the supercharger |4. Depending upon the location of the valve 50, it may be operated through a suitable Bowden wire or by electromagnetic control means instead of by the handle 54 shown in Fig. 2.

In using the system of Fig. 2, the valve will normally be in its full-line position so that the products of combustion are discharged overboard, but under such conditions where high output of heat from' the heater is essential, and such high output is not obtainable due to the low difference in pressure between the pressure side of the supercharger |4 and the atmosphere, the pilot may shift the valve 52 to its dotted-line position,

' thus utilizing the full diierential pressure across the supercharger |4 to assurev an adequate supply of combustible mixture to the heater.

While we have shown and described a particular embodiment of our invention, it will be apparent to those skilled in the art that the essential features thereof rnay be embodied in varied and modified forms.' We therefore desire to include within the scope of the following claims, all such modications and variations of the inventlon whereby substantially the results of the invention maybe obtained through the use of substantially the same or equivalent means.

We claim:

1. In an airplane having a supercharger for supplying a mixture of fuel and air to the engine, the combination of a heater of the internal combustion type, means for conducting a fuel and air mixture from the pressure side of said supercharger to said heater for combustion therein, a conduit for conveying products of combustion from said heater, a three-way connection having one port receiving products of combustion from said last named conduit, a conduit connecting conduit 28 or the conduit 26, depending upon of said three-way connection, a conduit connecting the third port of said three-Way connection to the atmosphere, valve means controlling ow from the three-way connection to the supercharger inlet conduit responsive to the differential of pressures therebetween, and separate valve means controllingv ow from the three-way connection to the atmosphere conduit responsive to the diierentials in pressure therebetween.

2. In an airplane having a supercharger for supplying a mixture of fuel and air to the engine, the combination of a heater of the internal conibustion type, means for conducting a fuel and air mixture from the pressure side of said supercharger to said heater for combustion therein, a rst conduit for conveying products of combustion from said heater, a valve body having three ing the third port of said valve body to the atmosphere, and loaded check valves in said second and in` said third conduits,- said check valves being arranged to open to pass the products of v combustion to whichever of said second-and third conduits is at the lower pressure.

3. In an airplane having a supercharger for supplying a mixture of fuel and air to the engine, the combination of \a heater ofthe internal combustion type, means for conducting a fuel and air mixture from the pressure side of said supercharger to said heater for combustion therein, an exhaust conduit for conveying products of combustionfrom said heater, valve means connected to receive products of combustion from said ex- 

